In the manufacture of semiconductor devices and other products, ion implantation systems are used to impart impurities, known as dopant elements, into semiconductor wafers, display panels, or other workpieces. Typical ion implantation systems or ion implanters treat a workpiece with an ion beam in order to produce n- or p-type doped regions, or to form passivation layers in the workpiece. When used for doping semiconductors, the ion implantation system injects a selected ion species to produce the desired extrinsic material. For example, implanting ions generated from source materials such as antimony, arsenic, or phosphorus results in n-type extrinsic material wafers. Alternatively, implanting ions generated from materials such as boron, gallium, or indium creates p-type extrinsic material portions in a semiconductor wafer.
FIG. 1A illustrates an exemplary ion implantation system 10 having a terminal 12, a beamline assembly 14, and an end station 16. The terminal 12 includes an ion source 20 powered by a high voltage power supply 22 that produces and directs an ion beam 24 through the beamline assembly 14, and ultimately, to the end station 16. The beamline assembly 14 has a beamguide 26 and a mass analyzer 28, wherein a dipole magnetic field is established to pass only ions of appropriate charge-to-mass ratio through an aperture 30 at an exit end of the beamguide 26 to a workpiece 32 (e.g., a semiconductor wafer, display panel, etc.) in the end station 16.
During ion implantation into the workpiece 32, various contaminants (not shown) are typically generated over time, wherein ions from the ion beam 24 strike various components 34, such as the aperture 30, along the beam path. Such collisions of ions with the various components 34, or even the workpiece 32 itself, can sputter contaminants (not shown) onto various situated surfaces along the beam path. Typically, the components 34 residing along the ion beam path are generally comprised of graphite, wherein the sputtered contaminants (not shown) are generally comprised of carbon, and possibly even some of the species of the ion beam 24 itself.
FIGS. 1B and 1C illustrate a conventional aperture 30, wherein contaminants 36 have been sputtered onto surfaces 38 of the aperture. Over time, the contaminants 36 grow and build upon themselves, wherein a potential exists for portions of the contaminants (e.g., free contaminants 40) to eventually break free or flake off from the surfaces 38. Such free contaminants 40 may then travel with the ion beam 24, and be imparted onto the workpiece 30 of FIG. 1A. Such contamination of the workpiece 30 may lead to a failure of the resulting device(s) (not shown) formed on the workpiece, thus decreasing the efficiency and product yield of the ion implantation system 10.
A continuing trend toward smaller electronic devices has further presented an incentive to “pack” a greater number of smaller, more powerful and more energy efficient semiconductor devices onto individual wafers. This necessitates careful control over semiconductor fabrication processes, including ion implantation, and more particularly, necessitates a minimization of contaminants imparted onto the workpieces during ion implantation. Moreover, semiconductor devices are being fabricated upon larger and larger workpieces in order to increase product yield. For example, wafers having a diameter of 300 mm or more are being utilized so that more devices can be produced on a single wafer. Such wafers are expensive and, thus, make it very desirable to mitigate waste, such as having to scrap an entire wafer due to contaminants imparted to the wafer during ion implantation.
As a consequence, contamination formed on surfaces within the ion implanter 10 of FIG. 1A is conventionally removed by a manual cleaning of the various components 34 by an operator during scheduled maintenance of the ion implantation system. Such manual cleaning is costly, not only in terms of time and labor attributed to the operator, but also in terms of decreased efficiency and yield of the ion implantation system 10 due to increased down-time associated with the maintenance. As an alternative, reactive gases (not shown) have been introduced into the ion implantation system 10 in an attempt to remove the contamination by chemical reaction between the contaminants and the reactive gases. This solution, however, typically requires a change of gases in the ion implanter 10, wherein the source material gas used for implanting ions into the workpiece 30 is purged from the ion implanter, the reactive gas is then used to remove the contamination, and then the reactive gas is further purged from the implanter prior to processing another workpiece. Such a change of gases, however, may decrease the efficiency of the ion implantation system 10, thus decreasing a throughput of the implanter.
Accordingly, a need currently exists for an improved ion implantation system cleaning method, wherein efficient contaminant removal can be facilitated, and wherein the cleaning method can be performed in-situ using the same source material gas used to implant ions into the workpiece, wherein high throughput and highly reliable ion implantation into a workpiece can be achieved.